emissions tuning

I'm looking to buy an exhaust from headers back, I'm worried about meeting the requirements for emissions though. I live in Idaho. I want as much horsepower for the price as I can get as well. I'd prefer a titanium one but I don't have my heart set yet. I like deep sounds without it sounding...

Vendors - here's what I want to accomplish with this thread - there are people on here who are interested in determining what kits they can use and still pass OBDII-based emissions testing. For example, I'm in NY, and I don't "know a guy" so any upgrades would have to be compatible...